Declutter the background, zoom in tight to eliminate background "distractions", or change your angle so your subject remains the focus of the image
Use architectural lines - walls, fences, roads, or any lines to lead the eye through the photograph and draw attention toward the main subject.
The red sideline lead us to the main subject, the student. However if the backgound was slightly blurred it would give the subject more focus. His face may not be very clear and his white sweater washes him off a bit. The orange shirt underneath could have centered the attention more on him. Other than that the line do thier job as the direct us to the student.
Rule of Thirds
Frame your image with the subject off center it's more pleasing to the eye and appears more natural than placing the subject in the center.
Create a sense of movement by adding active space (the area your subject is facing) and eliminating dead space (the area behind your subject).